Launch-In-SITL.md

 ## Setup workspace
-First, create a catkin workspace OR use existing catkin workspace (If you have realsense-ros setup)
+First, create a catkin workspace OR use existing catkin workspace (If you have realsense-ros setup).
+
+**ONLY** do this if you don't have a catkin workspace, otherwise use the existing one
 ```shell
 mkdir -p ardupilot_ws/src
 cd ardupilot_ws